The invention relates generally to materials for sealing, isolating, treating or minimizing erosion of a surface, and more particularly to hydratable composite particles which are effective for these and other applications.
A significant number of lakes, ponds, reservoirs, lagoons, marshes, river beds and ocean areas near coastlines are contaminated with environmentally hazardous materials. Examples of such materials include polychlorinated biphenyls (xe2x80x9cPCB""sxe2x80x9d), white phosphorus, synthetic organic compounds, and various metals. Many of these materials, once introduced by one means or another, settle on the bottoms of such bodies of water and become attached to sediments. The resulting contaminated sediments are detrimental to the ecosystem, especially wildlife which utilizes the body of water, such as fish, foraging waterfowl and small vertebrates and invertebrates. In some cases the contaminants are slowly released from the sediments and re-introduced into the water column. Such sediment-borne contaminants can also adversely impact wetland or deepwater ecosystems indirectly through food-chain effects.
In some cases, it is not feasible to remove or treat such contaminated sediments in place, or in situ. Thus, to restrict wildlife and other organisms from coming into contact with the contaminated sediments and to seal or isolate the sediments from coming into contact with the water column, it has been proposed to form an underwater barrier layer over the contaminated sediments. Previous methods have been relatively difficult and expensive to install, and have been susceptible to damage. Thus, an effective method of sealing or isolating the contaminated sediments is needed. Preferably, an effective method would also be beneficial in minimizing leakage losses from the surface-water body, and in minimizing potential impacts to ground water when the water body contains dissolved contaminants.
Contaminated sediments occur in wetland as well as deepwater (non-vegetated) environments characterized by freshwater or saline (including brackish) conditions. Remedial dredging and removal of sediments is an often used ex-situ approach for addressing this issue. A number of environmental impacts are known to be associated with remedial dredging, including re-suspension of contaminated sediments into the overlying water column and incomplete removal of sediment contaminants from the uppermost, and most biologically active, layers. Remedial dredging of wetland sediments, in particular, could also severely impact or destroy a wetland ecosystem and compromise related wetland functions. Therefore, other less-invasive but equally effective remediation technologies, or alternatives, for addressing contaminated sediments in deepwater or wetland environments are needed.
High-flow conditions can periodically occur along a variety of manmade and naturally occurring waterways, including along drainage ditches or channels, near culvert inlets and outfalls, and in some riverine environments. Such conditions can result in significant scour and erosional losses of exposed bottom substrates. Erosion of basal substrates can also subsequently result in failure of the conveyance system and, in some cases, detrimental buildup of displaced and re-deposited sediments in downstream locations. An effective method for erosion control is needed.
When subsurface pipelines (including culverts) are installed, the pipelines are typically bedded in stone or sand bedding material that can act as a conduit for the migration of water and/or contaminants. In the case of pipelines piercing a dam or levee, a continuous hydraulic (low-permeability) seal is required between the pipe and its immediate surroundings; such a seal minimizes the potential for leakage of municipal water supplies. In the case of contaminated site remediation, sewage, petroleum products, or other contaminants can flow through the bedding material into adjacent geologic or soil material. The greatest potential for leakage typically occurs at joints between pipe sections, although leakage can also occur along the pipe body, where cracks or ruptures have developed. Effective pipeline sealing also minimizes the potential for movement of ground waters or other fluids into the conveyance structure, which could have particular relevance in areas where ground water tables are high (such as in wetlands) and/or where ground water is contaminated. An effective method for pipeline sealing is needed.
A low-permeability, hydraulic seal is also required during the construction of ground water monitoring and extraction wells and in the petroleum and brine drilling and extraction industry to minimize the potential for vertical transfer of contaminated ground water, oil, or brine along the well""s annular space. Such transfers could result in pollutant migration into adjacent aquifers.
Landfill sites are typically constructed by completing an excavation in the ground and lining the excavation to form a containing system prior to filling with waste materials. Unfortunately, the landfill is susceptible to leaching contaminants into the surrounding ground and possibly into the water table. The upper surface of the landfill attracts pests such as birds and rodents which can possibly carry diseases.
This invention relates to a method of creating a seal in a subsurface environment. In the method, a plurality of manufactured composite particles are placed in the subsurface environment, the composite particles including a sealant material. The sealant material is hydrated to create a cohesive seal.
The invention also relates to a method of controlling erosion of a periodically or continuously inundated surface. In the method, a plurality of manufactured composite particles are placed around erosion-control objects. The composite particles include a sealant material which is a cohesive, low-permeability material when hydrated. The sealant material physically stabilizes the erosion-control objects on the surface.
The invention also relates to a method of applying a flowable material to form a sealant layer on an underwater surface including contaminated sediments. The flowable material comprises a plurality of manufactured composite particles including a sealant material. In the method, a layer of sand-sized material or other material is applied over the surface prior to applying the composite particles to reduce sediment re-suspension upon particle impact, and to minimize penetration and settling of particles into the surface.
The invention also relates to a flowable material comprising a plurality of manufactured composite particles. Each composite particle comprises a core, and a sealant layer at least partially encapsulating the core. The sealant layer comprising sealant material capable of at least one of absorbing water, swelling, and reacting. The core is less dense and softer than the sealant layer. The composite particle has a specific gravity greater than one.
The invention also relates to another embodiment of a flowable material comprising a plurality of manufactured composite particles. Each composite particle comprises a core and a sealant layer at least partially encapsulating the core. The sealant layer comprises sealant material capable of at least one of absorbing water, swelling, and reacting. The sealant layer comprises a combination of a clay mineral and other material comprised of quasi clay-sized particles, the quasi clay-sized particles having an average particle size of less than about 10 microns.
The invention also relates to another embodiment of the flowable material. In this embodiment, the sealant layer comprises a combination of sand-sized material and at least one of a clay mineral and another material comprised of clay-sized particles.
The invention also relates to another embodiment of the flowable material. In this embodiment, at least one of the core and the sealant layer contains an oxidizing agent.
The invention also relates to another embodiment of the flowable material. In this embodiment, the sealant layer forms a barrier layer having a low permeability, and the presence of significant quantities of core material in the barrier layer has an insignificant effect on the permeability of the barrier layer.
The invention also relates to another embodiment of the flowable material. In this embodiment, the sealant layer forms a barrier layer having a permeability of less than about 1xc3x9710xe2x88x926 cm/sec in saline conditions.
The invention also relates to another embodiment of the flowable material. In this embodiment, the sealant layer forms an underwater barrier layer which is substantially resistant to water flow velocities within a range from about 1 ft/sec to about 6 ft/sec.
Various objects and advantages of the invention will become readily apparent to those skilled in the art from the following detailed description of preferred embodiments when considered in the light of the accompanying drawings.